Bill Tindall, E.Tn.
Corner cupboards from an earlier time were larger, hence larger glass in doors, but with somewhat larger frames.

I saw no reason to be concerned with glass weight. The cabinet frame is a ridged structure and it will not move. The door is made with hand made deep mortise and tenon joinery. I can't see these joints failing from the glass weight. The doors have 3 tight fitting brass hinges, properly mortised into the framing. The hinge mortises are not going to allow the hinge to move for they support the weight, not the screws, which only hold the hinge in the mortise. The whole of it seems secure.